The present invention relates to an obstacle-detecting apparatus which is adapted to detect an obstacle such as a vehicle stopped in trouble at a railroad crossing.
FIG. 5 shows a conventional obstacle-detecting apparatus installed at a railroad crossing. As shown, a numeral 51 denotes a control unit. A numeral 52 denotes a beam emitter. A numeral 53 denotes a beam receptor. A numeral 54 denotes a processing unit. A numeral 55 denotes a signal conditioning that a train comes closer to the crossing, which signal is entered into the control unit 51. A numeral 56 denotes a laser beam emitted from the beam emitter 52. A numeral 57 denotes an information indicating that an obstacle is detected. A plurality of pairs of the beam emitter 52 and the beam receptor 53 are installed at one railroad crossing.
Next, the description will be directed to how the obstacle-detecting apparatus shown in FIG. 5 operates. In response to the conditioning signal 55, the control unit 51 issues a command to the beam emitter 52 so that the beam emitter 52 may output the laser beam 56. In response to the laser beam 56, the beam receptor 53, installed in opposed relationship to the beam emitter 52 with the railroad laid therebetween, operates to output a signal to the processing unit 54. The processing unit 54 has a function of determining whether or not the beam receptor 53 outputs the signal. If no signal is received from the beam receptor 53 for a certain length of time, the processing unit 54 determines that any obstacle standing on the railroad between the beam emitter 52 and the beam receptor 53 impedes the laser beam 56 and thereby outputs the obstacle-detected information 57 to a next stage (not shown).
As set forth above, the conventional obstacle-detecting apparatus may have an arrangement that several pairs of the beam emitter and the beam receptor are installed at a railroad crossing for the purpose of detecting as an obstacle a vehicle stopped in trouble at the railroad crossing.